For those more knowledgeable. Are emission limits calculated similarly for all countries. Is it: calculate current emission, set allowance for next year as pre

For those more knowledgeable. Are emission limits calculated similarly for all countries. Is it: calculate current emission, set allowance for next year as prev_year_emission * 0.99 (or some other reduction)? This equation would need modifications for richer and poorer countries (which can't modernize so easily) Is that similar to how those limits are set? Or all all countries set to some arbitrary limits - that would explain those emission purchases.